1. Field of the Invention
The present invention relates generally to an electromagnetic sensing apparatus built in a touch screen having at least one soft key, and more particularly, to an electromagnetic sensing apparatus for sensing an external input from a user by sensing ElectroMagnetic Resonance (EMR).
2. Description of the Related Art
Extensive research has recently been conducted on smart phones and touch screens. A user can input a specific command to a smart phone or a touch screen by selecting a specific position or icon on the display of the smart phone or touch screen with a user's body part or an EMR pen.
The former scheme can be implemented in a capacitive type. In general, a capacitive touch screen includes transparent electrodes and condensers. As the user touches the touch screen, a mechanical displacement may be caused to the space or area of a built-in condenser. The touch may be sensed based on the resulting changed capacity of the condenser.
However, the capacitive type requires a specific pressure or displacement caused by a user's touch, thereby resulting in user inconvenience. In this context, EMR is a recent active study area.
An EMR type controls generation of electromagnetic waves by flowing current through a loop coil disposed on a Printed Circuit Board (PCB) and controls absorption of the electromagnetic waves into an EMR pen. The EMR pen may include a condenser and a loop and emit the absorbed electromagnetic waves in a specific frequency.
The electromagnetic waves emitted from the EMR pen may be absorbed again into the loop coil of the PCB so that a position near to the EMR pen can be determined based on the absorbed electromagnetic waves.
FIGS. 1A, 1B and 1C illustrate a conventional EMR scheme.
FIG. 1A illustrates a communication device 100 with an electromagnetic sensing apparatus operating in the conventional EMR scheme. Referring to FIG. 1A, the communication device 100 may include a display 110 and soft keys 120.
The display 110 may display information visually to a user. The display 110 may operate in either of an EMR scheme and a capacitive scheme.
The soft keys 120 are a type of user interface provided separately from the display 110, which enables the user to intuitively perform basic functions such as back, cancel, menu display control, etc. Conventionally, the soft keys 120 operate only in the capacitive scheme due to limitations on accommodation of capacitive sensors and EMR sensors arranged under transparent electrodes. Soft keys having EMR sensors built in them have not been specified yet.
FIG. 1B illustrates a plurality of loops 131 to 134 arranged in the display 110. Referring to FIG. 1B, the plurality of loops 131 to 134 may be arranged overlapping with each other. When the user places an EMR pen close to a specific position, the loops 131 to 134 may sense an electromagnetic field from the EMR pen.
Referring to FIG. 1C, each of the loops 131 to 134 may output current induced by the sensed electromagnetic field. A loop nearer to the EMR pen may sense a large-amplitude electromagnetic wave and emit induced current corresponding to the sensed electromagnetic wave. Therefore, induced current with different magnitudes may be output as illustrated in FIG. 1C.
A microprocessor of the communication device 100 may determine a peak by interpolating the magnitudes of the output induced current and thus may determine a user-input position on the display.
Since only the capacitive scheme is adopted for the soft keys 120, the user should input commands by touching the soft keys 120 with his or her body part.
If channels are added to sense EMR on the soft keys 120, the numbers of channels and coils are increased. As a result, a control circuit increases in size, causing an increase in production cost.